The present invention relates to a semiconductor structure, and particularly to a transmission line structure providing a reduced phase velocity for a radio frequency signal such as a millimeter wave, a design structure for the same, and methods for operating the same.
Millimeter waves refer to electromagnetic radiation having a wavelength range from about 1 mm to about 10 mm. The corresponding frequency range for millimeter waves is from about 30 GHz to about 300 GHz. The wavelength range for the millimeter waves occupies the highest frequency range for microwaves, and is also referred to as extremely high frequency (EHF). The frequency range for the millimeter waves is the highest radio frequency band, and the electromagnetic radiation having a higher frequency than the millimeter waves is considered to be a far end (a long end) of the infrared radiation.
Millimeter waves display frequency-dependent atmospheric absorption due to oxygen and water vapor. The absorption coefficient for oxygen in atmosphere ranges from about 0.01 dB/km to about 10 dB/km, and the absorption coefficient for water vapor in atmosphere ranges from about 0.03 dB/km to about 30 dB/km. Due to the atmospheric absorption, the strength of a millimeter wave signal decreases more with distance than radio frequency signals at lower frequency.
While attenuation characteristics of millimeter waves limit the range of signal communication, the rapid signal attenuation with distance of the millimeter wave also enables frequency reuses. In other words, an array of millimeter wave signal transmitters may share the same frequency range for a subset of millimeter wave signal transmitters that are separated from each other by a sufficient distance. For this reason, millimeter waves are employed for short range radio communication including cellular phone applications.
Due to the short wavelength of the millimeter waves, manipulation of millimeter waves such as phase modulation poses a challenge in semiconductor devices.